Americans typically gain a pound between Thanksgiving and New Year’s Day. That may not sound like much to worry about, but the problem is that we don’t lose that pound once the holiday season ends. Instead, we accumulate a pound per season, year after year, for 10, 15, 20 years and more. Looked at that way, it’s no wonder that two-thirds of Americans are now obese.

So all we have to do, rather than gaining that pound, is lose a pound during the holidays — or just stay even. It’s only six weeks, so let’s show some discipline and skip the gravy, plum pudding and eggnog. It seems simple enough, but alas it’s not, as any dieter will tell you. Showing restraint during the holidays is so much harder than it is normally, even with the best intentions.

Some intriguing new evidence from the University of Chicago suggests that dieters may be fundamentally different in their response to temptation — in a way that actually increases risk of gaining weight during the holidays. The abundance of sweet and savory sights and aromas may trigger a pleasurable response that doesn’t abate in the normal way, persisting through time and sabotaging self-discipline.

At least that’s the theory of psychological scientist Wilhelm Hofmann, who with his colleagues has been exploring the interplay of temptation, restraint, pleasure and time. They studied a large group of volunteers, some of whom were always vigilant about their diet; the others were lucky and didn’t have to exercise restraint. Some of these volunteers were primed with a food stimulus — the thought of chocolate or cake, for example — while others were not. The scientists wanted to see if the dieters who were exposed to thoughts of rich food — the equivalent of having holiday aromas wafting through the home — would later have a more emotional reaction to these tempting foods.

They predicted that without the priming, the dieters’ goals and motivation to succeed would be strong enough to trump any extraordinary pleasure response. And that’s just what they found. Without exposure to the idea of rich food, the dieters did just fine with self-restraint; indeed their emotional response to food was actually less intense than that of the non-dieters. But here’s the rub: When primed with visions of sugarplums and other temptations, the dieters had a much more elevated and enduring emotional response to tempting food. The non-dieters also experienced good feelings when stimulated by thoughts of holiday food, but their pleasure dissipated rapidly, whereas the dieter’s pleasure response showed no sign of dropping off. In other words, the food-rich environment put them in a “hot” state, which not only put them at greater risk of abandoning their dietary goals, but kept them in that “hot” state.

In order to better understand this “hot” state, the scientists gave the volunteers two additional questionnaires. One measured the power of food with items like: “If I see or smell a food I like, I get a powerful urge to have some.” The other one was a food cravings questionnaire, which measured things like intensity of craving; eating to salve negative emotions and lack of control over eating. Both of these questionnaires tap into attitudes and feelings related to problem eating. And, as reported online in the journal Psychological Science, both these measures were closely connected to the dieters’ unflagging pleasure around rich food.

The normal eaters in these studies — which really means the lucky minority who don’t have to diet — are scientifically interesting. They appear to have a pleasurable response to food, but one that naturally diminishes over time, hinting at some kind of internal mechanism for disengaging from familiar smells, tastes and other tempting cues. Those of us who lack that normal control have a more elaborate and unhealthy relationship to food as a source of pleasure — what has been called “hedonic hunger” — which makes the temptation-rich holiday home a dangerous place.